1. Field of the Invention
The present invention relates to a charge transfer multi-linear strip.
2. Descrption of the prior art
Such strips are known in the prior art which will be described with reference to FIGS. 1 and 2.
In these strips, N aligned photosensitive elements are used, called D.sub.1, D.sub.2 . . . D.sub.N in FIG. 1. These N photosensitive elements receive successively the radiation to be detected.
In FIG. 1, an arrow going from left to right shows the direction in which the strip travels in front of the object or body 1 which is emitting the radiation to be detected. The integration time is thus multiplied by a factor N provided the information collected by the different detectors is summed in synchronism with the travelling movement. For summing in phase the information collected, this information must be provided with delays of values T, 2T, 3T . . . NT, where T is the time for the passage of the object or body which is emitting the radiation in front of each detector, it is also the integration time of each detector. In FIG. 1 is shown schematically that a delay T is provided for the information coming from detector D.sub.1 before being fed to a summator, a delay 2T is provided for the information coming from detector D.sub.2 . . . and so on.
The device shown in FIG. 1--apart from the detectors D.sub.1 to D.sub.N --is known under the name of "time delay integration" or TDI and it is by these initials that it will be mentioned hereafter.
Constructing a TDI from a charge transfer shift register with parallel inputs and a series output is known. In the example shown in FIG. 1, the information coming from detector D.sub.N is fed to the first stage of the register, then is transferred to the second stage where it is summed with the information coming from detector D.sub.N-1 . . . and so on.
The U.S. Pat. No. 4,054,797 shows a TDI, for infra-red radiations, comprising transfer shift registers with parallel lateral inputs and a series output, the stages of these registers having a capacity increasing in the direction of the charge transfer. It is explained in this U.S. Pat., column 4, lines 6 to 12, that the information is fed to the TDI in voltage form, that is to say that the charges stored in the detectors are read as voltages and it is these voltages which control the injection of the charges into the TDI.
For forming a charge transfer multi-linear strip of great dimensions, for example 30 cm, in length, for radiology, a large number of devices such as the one shown in FIG. 1 are used. On a support, M circuits each comprising N detector lines and P detector columns are juxtaposed, with the N detectors of the same column connected to a TDI as shown in FIG. 1.
Thus, for example, a strip 50 cm in length is obtained, formed from M=50 elementary strips each comprising P=40 detector columns, and 1 cm in width, with N, the number of lines, equal to 20.